In integrated circuit (IC) fabrications, a patterned photoresist layer is used to transfer a designed pattern having small feature sizes from a photomask to a wafer. The photoresist is light-sensitive and can be patterned by a photolithography process. Furthermore, the photoresist layer provides resistance to etch or ion implantation, which further requires a sufficient thickness. During a lithography patterning process, the photoresist is exposed and developed to form a patterned photoresist layer. To reduce feature size and increase pattern density, multiple patterning techniques are used in advanced technology nodes, which changes relative pattern density photoresist in each patterning. However, after the formation of the patterned photoresist layer, some defects, such as water stains and solvent remains, are formed thereon, reducing the image quality and causing patterning issues. This is more problematic to advanced technology nodes and multiple patterning processes.
Therefore, there is need for a lithography method to address the above issues.